The design optimization through modeling of a thinned bulk-PZT-based vibration energy harvester on a flexible polymeric substrate is presented. We also propose a simple foil-level fabrication process for their realization, by thinning the PZT down to 50 mu m and laminating it via dry film photoresist onto a PET substrate at low temperature (<85 degrees C). Two models, based on analytical and finite element modeling (FEM) methods, were developed and experimentally validated. The first, referred to as the hybrid model, is based mainly on analytical equations with the introduction of a correction factor derived from FEM simulations. The second, referred to as the numerical model, is fully based on COMSOL simulations. Both models have exhibited a very good agreement with the measured output power and resonance frequency. After their validation, a geometrical optimization through a parametric study was performed for the length, width, and thicknesses of the different layers comprising the device. As a result, an output power of 6.7 mu W at 49.8 Hz and 0.1 g, a normalized power density (NPD) of 11 683 mu W g(-2) cm(-3), and a figure of merit (FOM) of 227 mu W g(-2) cm(-3) were obtained for the optimized harvester.